JP2729973B2 - Rubber composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition suitable as a tire tread member for passenger cars and light trucks, and more particularly to a low heat build-up which has both excellent wear resistance and high rebound resilience effective for fuel-efficient tires. And a rubber composition.

[0002]

2. Description of the Related Art There are various types of carbon blacks for reinforcing rubber according to their characteristics, and the characteristics of these types are major factors for determining various properties of a composition mixed with rubber. For this reason, when compounding with rubber, a means for selecting and using carbon black having a variety of characteristics suitable for the purpose of the member is generally used.

[0003] For example, in recent years, fuel-efficient tires have been actively developed to meet the social demands for resource saving and energy saving, but such fuel-efficient tires have a relatively small particle size. A rubber composition having low heat build-up and high rebound resilience in which a large variety of carbon black is blended in a relatively small amount into a rubber component is effective. However, rubber compounding of carbon black with a large particle diameter and a small specific surface area is effective for the purpose of improving fuel economy performance,
Deterioration of surface characteristics such as braking performance and abrasion resistance on wet road surfaces is inevitable. Therefore, if carbon black having a small particle size and a large specific surface area can be simultaneously imparted to a compounded rubber with high abrasion resistance and low heat generation giving high rebound resilience, a tire tread intended for low fuel consumption can be provided. It becomes ideal as a rubber member for use.

[0004] The applicant of the present invention adds the above-mentioned reciprocal rubber performance to the characteristic aspects of the carbon black to be compounded, in particular, to the basic properties such as particle diameter, specific surface area, structure and the like, as well as more microselective properties. We have systematically continued the research to make this compatible, and have already made the following development proposals. (1) Nitrogen adsorption specific surface area (N ₂ SA) is 60 m ² / g or more, compressed DBP
A carbon black that can simultaneously impart high reinforcement performance and high rebound resilience to a compounded rubber in which the Stokes mode diameter and the distribution of aggregates are maintained at a certain value or more in a carbon black of 112 ml / 100 g or more (Japanese Patent Publication No. (No. 53978)
. (2) N ₂ SA 60 m ² / g or more, DBP 108 ml / 100 g or more, the true specific gravity per specific surface area is set to a specific range that is significantly lower than that of known carbon black, and the coloring power and distribution per aggregate mode diameter are set. A rubber composition having high abrasion resistance and high rebound resilience blended with carbon black for maintaining the width at or above a certain value (Japanese Patent Laid-Open No. 59-140241). (3) N ₂ SA is 65 to 84 m ² / g, N ₂ SA / Iodine adsorption amount (I
The ratio of A) is in the range of 1.10 to 1.35, and the abrasion resistance and the high wear resistance of the compounded rubber whose compression formula DBP, blackness, iodine adsorption amount and agglomerate mode diameter as variables are set to a certain value or more are set. Carbon black capable of simultaneously providing rebound resilience (Japanese Patent Application Laid-Open No. 62-58792). (4) When the N ₂ SA is 75 to 105 m ² / g, the compressed DBP is 110 ml / 100 g or more, the true specific gravity per specific surface area is set to a specific range lower than that of known carbon black, and the particle aggregate void diameter And carbon black (Japanese Patent Laid-Open No. 1-201367) which can combine high abrasion resistance and high rebound resilience with a compounded rubber having a distribution width per aggregate mode diameter of a certain value or more.

[0005] In addition, US Pat. No. 4,360,627 discloses N ₂ SA 85 to 95 m ² / for tire tread rubber.
g, 24M4DBP 100-104ml / 100g, Tint 95-105%
And the distribution of aggregate Stokes mode diameter (△ D ₅₀ ) is 180m
A carbon black achieving high wear resistance and high rebound resilience of at least μ has been disclosed, and U.S. Pat.
No. The specification, as the carbon black characteristics to obtain a high degree of wet grip performance low rolling resistance and required energy savings for a tire tread rubber, N ₂ SA75~
105m ² / g, N ₂ SA-IA ≧ 15, N ₂ SA-CTABS
A ≦ 5, 24M4DBP ≦ 110, Tint 90-110, ΔTint
≦ −3 is indicated.

The present inventors have developed a rubber composition having a high level of rebound resilience and abrasion resistance suitable for use in fuel-efficient tires even more than the above-mentioned prior art, and having a nitrogen adsorption specific surface area (N ₂ SA). Belongs to a hard region of 60 to 100 m ² / g, and the mode diameter (Dp) of the pores between the aggregate grains is Dp ≦ 1.543 ×
(Dst mode diameter) −55.0] was added to 35 to 10 parts by weight of rubber component 100 parts by weight.
A composition comprising 0 parts by weight was developed and proposed as Japanese Patent Application No. 2-340732.

[0007]

However, the demand for materials for fuel-efficient tires is becoming more and more advanced, and it is currently difficult for the rubber composition according to the prior invention to meet the recent required performance. It is.

[0008] The inventors of the present invention have succeeded in developing research on such a background and found that the nitrogen adsorption specific surface area (N ₂ SA) is 60 to
A furnace carbon black belonging to a hard system region having a compression DBP of 100 m ² / g or more and 110 ml / 100 g or more, wherein the mode diameter of aggregate intergranular pores is smaller than that of carbon black known so far. Med-al different from
Da defined by ia = [(2540 + 71 × DBP) / N ₂ SA]
It has been clarified that a rubber composition containing carbon black having a value less than or equal to a certain relational expression in relation to the value can obtain rubber properties suitable as a tire tread for passenger cars and light trucks.

The present invention has been developed on the basis of the above facts, and has an object to provide a high level of wear resistance and rebound resilience suitable for use in treads of fuel-efficient tires for passenger cars and light trucks. An object of the present invention is to provide a rubber composition having both of the above.

[0010]

The rubber composition according to the present invention for achieving the above object has a nitrogen adsorption specific surface area (N ₂ S
A) is a hard carbon region of 60 to 100 m ² / g, a compressed DBP of 110 ml / 100 g or more, and 35 to 100 parts by weight based on 100 parts by weight of a rubber component of furnace carbon black having selective properties according to the following relational expression. It is a structural feature that it is blended in the ratio of parts. Dp mode diameter ≦ 0.818 Da-12.87 where Dp mode diameter is the mode frequency of the maximum frequency in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and Da is [(2540+
71 × DBP) / N ₂ SA].

The values obtained by the following measuring methods are used for the respective characteristics of the carbon black having the above-mentioned structure. Nitrogen adsorption specific surface area (N ₂ SA); ASTM D3037-88 “Standard Test Method for C
arbon Black-SurfaceArea by Nitrogen Absorption ”M
According to ethodB. The measured value of IRB # 6 by this method is 7
6 m ² / g. Compressed DBP; ASTM D3493-85a “Standard Test Method for C
arbon Black- Dibutyl Phthalate Absorption Number of
DBP; JIS K6221 (1982) "Test method for carbon black for rubber", section 6.1.2, oil absorption A method. The measured value of IRB # 6 by this method is 99.0 ml / 100 g.

Dp mode diameter: After drying according to JIS K6221 (1982) 5 "How to make a dry sample", a carbon black sample precisely weighed is mixed with distilled water to obtain a paste having a carbon black concentration of 0.250 g / cm ³ . And disperse it sufficiently with ultrasound. Within 10 minutes after ultrasonic dispersion, differential scanning calorimeter (DSC, Mettler DSC)
At 30), measurement of the distribution of pores between aggregate grains is started. In this case, the amount of the collected paste is in the range of about 3 to 5 mg. After sealing in a sample container made of aluminum, the mass of the paste is confirmed, and the paste is set in the DSC device. Next, measurement is performed in the next step. Cool rapidly from room temperature to -80 ° C. Heat from -80 ° C to -5 ° C at a rate of 10 ° C / min. After heating from -5 ° C to -0.1 ° C at a rate of 1 ° C / min., -0.1 ° C (0.1 ° C lower than the freezing point of distilled water)
Hold for 10 minutes. Cool gradually from -0.1 ° C to -8 ° C at a rate of 0.1 ° C / min. And record the compensation energy. Then, the peak height (y) at each temperature (in increments of 0.1 ° C) is read from the compensation energy chart obtained in step (2), and the pore diameter (Dp) between the aggregate particles is obtained from the following equations (1) and (2). ) And pore size distribution (△ V / △ Dp). Dp = (135.34 / ΔT) +1.14 (1) ΔV / ΔDp = K · (ΔT) ² / (Wa × y) (2) In the equations (1) and (2), ΔT represents distilled water. The freezing point depression width, Wa is the heat of freezing of distilled water, and K is a factor taking into account the sensitivity of the DSC device and the mass of the sample. These formulas were derived by Brun et al.
ta, 21 (1977) 59-88 “A NEW METHOD FOR THE SIMULTANE
OUS DETERMINATION OF THE SIZE AND THE SHAPE OF POR
ES: THE THERMOPOROMETRY ”.
ASTM D-24 Standard Refe measured by this method
The Dp mode diameter of rence Black C-3 (N234) was 77.6 nm.

Furnace carbon black having the characteristics of the present invention is coaxially connected to a combustion chamber having a tangential air supply port at the furnace head and a combustion burner and a feed oil injection nozzle mounted in the furnace axis direction. It is manufactured by using a normal oil furnace composed of a narrow-diameter reaction chamber and a wide-diameter reaction chamber, and adjusting the supply amounts of raw oil, fuel oil, air, etc., and adding oxygen gas and other conditions. be able to.

The above-mentioned furnace carbon black is blended with an elastomer such as natural rubber, styrene butadiene rubber, polybutadiene rubber, isoprene rubber, butyl rubber, other various rubbers which can be reinforced with conventional carbon black, and mixed rubber according to a conventional method. The compounding ratio of carbon black is 35 to 100 parts by weight with respect to 100 parts by weight of the rubber component, and is kneaded together with necessary components such as a vulcanizing agent, a vulcanization accelerator, an antioxidant, a vulcanization aid, a softener, and a plasticizer. Thus, the rubber composition of the present invention is obtained.

[0015]

In the furnace carbon black characteristic items specified in the present invention, the nitrogen adsorption specific surface area (N ₂ SA) is 60 to 100 m ² /
g and the properties of the compressed DBP of 110 ml / 100 g or more belong to the hard system region, and are prerequisites for maintaining the compounded rubber with high abrasion resistance and moderate heat generation. If the nitrogen adsorption specific surface area is less than 60 m ² / g, the wear resistance becomes insufficient,
On the other hand, when it exceeds 100 m ² / g, the heat buildup increases, and it becomes difficult to use the carbon black for fuel-efficient tires. On the other hand, if the compression DBP is less than 110 ml / 100 g, not only is the abrasion resistance inadequate, but also a satisfactory effect cannot be obtained in terms of suppressing heat generation.

The mode diameter (Dp) of the aggregate intergranular pore is
It is a parameter indicating the properties of the aggregate (aggregate) in which carbon black is firmly fused and bonded, and is closely related to conditions such as the reaction temperature and the degree of disturbance of the combustion gas in the carbon black production process. For this reason, the carbon black has a correlation with the structure and the specific surface area. According to the study of the inventors, it has been confirmed that the general carbon black put on the market has the following formula (3). Dp mode diameter = (0.818 × Da−2.87) ± 9.2 (3) where Da is a value calculated by the following equation (4) defined by Medalia. Da = (2540 + 71 × DBP) / N ₂ SA (4) For example, ASTM D-24 Standard Reference Black
The measured Dp mode diameter of C-3 (N234) is 77.6 nm,
This falls within the range of the Dp mode diameter (63.3 to 81.7 nm) obtained by substituting the calculated value of Da (92.2) calculated from equation (4) into equation (3).

Therefore, Dp specified in the present invention is
The range of the mode diameter is further lower than the value calculated from the equation (3) in relation to Da, particularly [0.818 ×
Da-12.87], which is lower than or equal to the value calculated from the formula, and the unique property of this relatively small aggregate intergranular pore improves and improves the reinforcing performance and low heat generation of the compounded rubber composition. It is presumed that it is functioning.

The above-mentioned functions work together to make it possible for the rubber composition to have both excellent abrasion resistance and low heat generation to give high rebound resilience.

[0019]

Hereinafter, examples of the present invention will be described in comparison with comparative examples.

Examples 1 to 3 and Comparative Examples 1 to 3 A combustion chamber having a tangential air supply port at the furnace head and a combustion burner and a feed oil injection nozzle mounted in the furnace axis direction (diameter)
800mm, length 900mm), the first coaxially connected to the combustion chamber
An oil furnace was set up which consisted of a step narrow reaction chamber (diameter 250 mm, length 500 mm), a second step narrow reaction chamber (diameter 200 mm, length 500 mm), and a subsequent wide reaction chamber (diameter 400 mm). . The feedstock oil used was an aromatic hydrocarbon oil having a specific gravity (15/4 ° C) of 1.073, a viscosity (engler of 40/20 ° C) of 2.10, a toluene insoluble content of 0.03%, and a correlation coefficient (BMCI) of 140. A hydrocarbon oil having a specific gravity (15/4 ° C.) of 0.903, a viscosity (Cst / 50 ° C.) of 16.1, a residual carbon content of 5.4%, and a flash point of 96 ° C. was used.

Using the above-mentioned reactor, raw oil and fuel oil, three types of furnace carbon black were produced by changing the conditions of generation such as the amount of raw oil, the amount of fuel oil, the amount of air supply, and the presence or absence of oxygen gas. . Table 1 shows the conditions for generating carbon black and the characteristics of the obtained carbon black.
Displayed corresponding to o. Table 2 shows Comparative Examples 1 and 2.
The characteristics of the furnace carbon black which does not satisfy the characteristics requirements of the present invention and the characteristics of commercially available hard carbon black varieties are shown as Reference Examples 1 to 3.

[0022]

[Table 1] Table Note: 1) Mix and supply in combustion air 2) Calculation formula Dp mode diameter = [0.818Da -12.87], same hereafter

[0023]

[Table 2] Table Notes: 1) N351 [Tokai Carbon Co., Ltd., Seast NH] 2) N347 [Tokai Carbon Co., Ltd., Seast 3H] 3) N339 [Tokai Carbon Co., Ltd., Seast KH]

Next, these carbon black samples were compounded in styrene butadiene rubber [JSR1712, manufactured by Nippon Synthetic Rubber Co., Ltd.] at the compounding ratio shown in Table 3.

[0025]

[Table 3]

Each rubber composition obtained by vulcanizing the composition of Table 3 at a temperature of 145 ° C. for 50 minutes was subjected to various rubber tests, and the measured results were shown in Table 4 (Example) and Table 5 (Comparison). Example, Reference Example). In addition, the measurement of the rubber property was based on the following. Using a Lambourn abrasion tester (mechanical slip mechanism)
The measurement was performed under the following conditions. Test piece: thickness 10mm, outer diameter 44mm Emery wheel: GC type, particle size 80, hardness H Carborundum powder with addition: particle size 80 mesh, addition amount about 9
g / min. Relative slip ratio between emery wheel surface and test piece: 24%,
60% Test piece rotation speed: 535rpm Test load: 4kg

Tan δ (loss coefficient) Measured using a Visco Elastic Spectrometer manufactured by Iwamoto Seisakusho under the following conditions. Test piece: thickness 2 mm, length 30 mm, width 5 mm Frequency: 50 Hz Dynamic strain rate: 1.2% Temperature: 60 ° C. Other properties According to JIS K6301 “Vulcanized rubber physical test method”.

[0028]

[Table 4]

[0029]

[Table 5]

From Tables 4 and 5, it can be seen that the results of the Examples are higher than those of Comparative Examples and Reference Examples, which have the same specific surface area and which do not satisfy the selective characteristic requirements of the present invention, while having the same or higher high abrasion resistance. It can be seen that tan δ (loss coefficient), which is an index of sex, is significantly reduced, and the rebound resilience is greatly improved. It can also be seen that other reinforcing properties are maintained at a high level.

[0031]

As described above, according to the present invention, a rubber composition having low heat build-up and having both excellent abrasion resistance and high rebound resilience by selectively controlling the micro characteristics of carbon black different from the prior art. Can be provided. Therefore, the present invention can be applied to a tire tread member for a passenger car or a light truck to achieve effective fuel saving.

Claims (1)

(57) [Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 60 to 100 m ² / g
Furnace carbon black having a compressed DBP belonging to a hard region of 110 ml / 100 g or more and having selective characteristics according to the following relational formula was added to 35 parts by weight of rubber component 100 parts by weight.
A rubber composition compounded in a proportion of up to 100 parts by weight. Dp mode diameter ≦ 0.818 Da −12.87 where the Dp mode diameter in the above equation is the mode frequency of the maximum frequency in the pore diameter distribution between carbon black aggregate particles measured by a differential scanning calorimeter (DSC), and Da is [ (2540 + 71 × DBP) / N ₂ SA].